This invention relates to a safety socket having an insulating casing with at least two insertion openings for the pins of a plug, the openings each containing a contact piece electrically connected to an outer connection terminal.
Some of the already known types of safety sockets are provided with a restraining device at the mouth of the insertion openings. One of them has at its front face a slide having two circular holes spaced at the same distance as the spacing between the pins of the plug. The said slide is resiliently biased by a spring towards a position in which the said circular holes and the insertion opening of the socket itself are not aligned, thus making it impossible to insert the pins of the plug. In order to insert these pins, the slide must be moved so as to align the holes with the insertion openings. If a person, particularly a child, moves the slide with his hand and inserts a metallic object he risks electrocution.
Other safety sockets are provided at the mouths of the insertion openings with little oscillating lugs in locking engagement, which can be unlocked only by the simultaneous insertion of the pins of a plug. Although offering more safety than the sockets mentioned in the first place, a person plugging in a plug with one finger inadvertently placed on a pin risks receiving an electric shock.
The object of this invention is to avoid these drawbacks and to provide a completely foolproof safety socket.
The invention achieves its object by providing a safety socket of the type mentioned at the beginning of this specification, characterized in that each insertion opening is tapered from its mouth inwards and, in each case, is defined by a fixed part whose face defining the insertion opening is substantially parallel to the direction of insertion, and by a swinging part, one of the parts defining an insertion opening being made of electrically conductive material and the other one being made of insulating material; in each case, adjacent to the parts made of conductive material and outside of the insertion opening, a resilient contact tongue, flexible transversally to the direction of insertion, is rigidly mounted at one end to the insulating casing and is electrically connected to the respective connection terminal; and, in each case, the swinging part of an insertion opening is kinematically connected by means of a stirrup or connecting rod with the resilient contact tongue corresponding to at least another insertion opening.
With the socket of this invention, when inserting only one pin or any metallic object, such as e.g. a nail, the swinging movement of the corresponding swinging part causes the electric connection of the contact piece in the other insertion opening.
The arrangement of this invention may be applied also to single-phase earthed sockets, three-phase sockets, sockets for plugs with cylindrical pins, sockets for plugs with plane pins, and combination sockets.